[issue22683] bisect index out of bounds issue

[Paul Ianas]

Paul Ianas added the comment:

Sure, it is your call. As said, this is rather an enhancement.

Still, if I were to decide, I would chose:
1. not to break the API = raise IndexError instead of ValueError in case hi 
is invalid.
2. to protect against illegal values: as said, if hi  0 bisect_* always 
returns 0 (whatever the searched value).
3. I would implement a single _range_check(_len, lo, hi) method to do this 
logic (DRY).

That being said, from my point of view this ticket can be closed.

--

___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue22683
___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue22683] bisect index out of bounds issue

[Paul Ianas]

New submission from Paul Ianas:

The precondition for all the bisect functions is implemented like this:

if lo  0:
raise ValueError('lo must be non-negative')
if hi is None:
hi = len(a)

Now, of course, if hi is given, and hi = 2 * len(a), then we get an 
IndexError. In case hi  0, we always get 0 as a result (even if the element is 
there).

I think it would be better to treat the hi in the precondition in the same way 
as the lo parameter: that means, raise a ValueError in case hi has an illegal 
value.

Disclaimer: of course, it makes no sense to give an illegal argument to that 
function; still, since lo is treated against illegal values, maybe it's better 
to do the same for hi.

At the same time, maybe moving the precondition code in a separate function 
(which raises a ValueError in case precondition is not met) makes more sense, 
for not repeating the same code in all bisect functions.

A small snippet which reproduces this:

from bisect import bisect_left

a = [1, 2, 3, 4]
idx = bisect_left(a, 2, 0, 10)  # 10  2 * 4
print(idx)

--
components: Library (Lib)
messages: 229750
nosy: Paul.Ianas
priority: normal
severity: normal
status: open
title: bisect index out of bounds issue
type: enhancement
versions: Python 2.7, Python 3.2, Python 3.3, Python 3.4, Python 3.5

___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue22683
___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com